GUWAHATI, India (Reuters) - At least 15 Indian train robbers looking to steal diesel from a freight carriage died Saturday after inhaling poison gas stored in another tank they accidentally broke open, police said.

A police patrol party said they found 30 other people lying unconscious on both sides of a forested train track in India's Assam state.

"We found many empty drums which they must have brought with them to fill with oil," a local police officer said by phone.

The train was earlier stopped by dozens of armed people who police believe were members of a gang which frequently steals crude oil from trains and pipelines carrying oil to refineries in the oil-rich state.